An undercarriage of this type includes at least four wheels, and in general includes six or eight wheels for a heavy transport aircraft, i.e. an aircraft weighing considerably more than 400 tons. The leg of such an undercarriage is naturally dimensioned accordingly, so that the recess for receiving the undercarriage when it is in the up position has to be long, and the structure of the aircraft must therefore be reinforced.
Reference may be made for example to Documents EP-A-0 492 685, EP-A-0 492 687, and EP-A-0 492 688.
Furthermore, the undercarriage leg and the associated bracing means are disposed such that considerable cutting forces are exerted on the shock-absorbing rod by the set of wheels when they bear against the ground, so that the leg has to be dimensioned accordingly to enable the sliding rod to slide normally under any circumstances.
Finally, the presence of a hinged longitudinal beam equipped with pairs of wheels (forming what may be referred to as a rocking bogie) makes it necessary to have a special linkage if, in the undercarriage up position, the beam is to be angularly positioned so as to be compatible with the desired compactness of the recess for receiving the undercarriage. To this end, in order to have a minimal recess height, it has been proposed to provide a linkage for turning the longitudinal beam over through 180.degree. before retracting the main landing gear assembly in question.
The technological background of the invention is also illustrated by Documents EP-A-0 361 549, U.S. Pat. No. 2,754,072, and FR-A-1 232 741.